WDPN33 PGTW 121500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 24W (KOMPASU) WARNING 
NR 010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.8N 116.4E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 244 NM SOUTH-SOUTHEAST OF HONG KONG
   MOVEMENT PAST 6 HOURS: WESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 21 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A VERY
LARGE (GREATER THAN 10 DEGREE DIAMETER) SYSTEM WITH DEEP CONVECTIVE
BANDING, PRIMARILY OVER THE SOUTHERN SEMICIRCLE, WRAPPING INTO A
LARGE, RAGGED LOW-LEVEL CIRCULATION CENTER (LLCC). A 121015Z SSMIS
37GHZ COLOR COMPOSITE MICROWAVE IMAGE INDICATES A WELL ORGANIZED
SYSTEM WITH TIGHTLY-CURVED BANDING WRAPPING INTO A DEFINED LLCC.
THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON EIR
IMAGERY AND THE SSMIS IMAGE. DUE TO THE VERY LARGE NATURE OF THIS
SYSTEM, GALE-FORCE WINDS EXTEND OUT ALONG THE PERIPHERY NEAR TAIWAN
AND SOUTHWEST OF LUZON. A 121300Z SHIP OBSERVATION AT 16.9N 116.3E,
115NM SOUTH OF THE CENTER, INDICATED SOUTHWESTERLY SURFACE WINDS AT
60 KNOTS. THE INITIAL INTENSITY OF 55 KTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON THE AGENCY DVORAK ESTIMATES AND THE SATCON
ESTIMATE. UPPER-LEVEL ANALYSIS INDICATES A MARGINALLY FAVORABLE
ENVIRONMENT WITH LOW TO MODERATE VERTICAL WIND SHEAR (VWS) OFFSET
BY STRONG EQUATORWARD OUTFLOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR)
ENTRENCHED OVER CHINA.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.5 - 55 KTS
   KNES: T3.5 - 55 KTS
   CIMSS SATCON: 54 KTS AT 121018Z
   CIMSS ADT: 43 KTS AT 121140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TROPICAL STORM (TS) 24W IS FORECAST TO TRACK
WESTWARD THROUGH THE FORECAST PERIOD UNDER THE STEERING INFLUENCE
OF THE STR. TS 24W WILL STRENGTHEN TO A PEAK OF 60 KNOTS BY TAU 12
THEN GRADUALLY WEAKEN AS VWS INCREASES. AS THE SYSTEM TRACKS OVER
HAINAN AFTER 24, IT WILL WEAKEN SIGNIFICANTLY WITH MORE RAPID
WEAKENING EXPECTED AS THE SYSTEM MAKES LANDFALL OVER VIETNAM AFTER
TAU 48. DISSIPATION WILL OCCUR BY TAU 96 AS THE SYSTEM TRACKS
INLAND.     

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE REMAINS IN TIGHT
AGREEMENT THROUGH TAU 36 WITH A 40NM SPREAD IN SOLUTIONS AT TAU 36.
THE MODELS DIVERGE AFTER TAU 36 BUT REMAIN IN GOOD AGREEMENT
LENDING HIGH CONFIDENCE TO THE JTWC FORECAST TRACK.  

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: HIGH
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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